You sound like a great manager/team lead. I think the obsession with 9-5 and whatever else it takes to get the job done is absurd in today's world.
The one is having fixed working hours and, as in the parent comment, compensating with extra leave if those hours are overstepped.
The other is working overtime whenever there is extra work that has to get done.
> obsession with 9-5 and whatever else it takes
You mean an obsession with "working 9-5 ALONG WITH whatever else it takes", not an obsession with "9-5" and a separate obsession with "whatever it takes".
If you are looking longer term, avoiding burnout and employee satisfaction will be a net positive. If you are looking short-term (12 months at most, but 3 months is more of a burnout limit), you may benefit from overworking people.